Methods and apparatuses of the type defined in the introduction are known in various embodiments from practice. In these methods, the filaments are spun with the help of a spinner and are laid down on a deposition surface, in particular on a conveyor belt and/or a screen belt to form the nonwoven fleece web. It is known that this nonwoven fleece web may be preconsolidated by water-jet consolidation. The water-jet treatment is usually performed from only one side of the nonwoven fleece web.
Thereafter, the preconsolidated filaments deposited and/or nonwoven fleece web is released from the screen belt and sent to a separate water-jet unit for water-jet consolidation and/or for hydraulic final consolidation. —At a high basis weight of the nonwoven fleece web above approx. 80 g/m2, in particular above 100 g/m2 and especially above 150 g/m2, it has been found that only at very high water pressures is it possible to preconsolidate the dense filament deposit and/or nonwoven down into the lower filaments. This is associated with a relatively high energy consumption. Moreover, this hydrodynamic preconsolidation compacts the nonwoven fleece web greatly. In the hydraulic final consolidation, the water jets then strike a relatively dense barrier that they must penetrate in such a way that the filaments become entangled with one another throughout the thickness of the nonwoven. In the case of nonwoven fleece web of a higher basis weight in particular, an elevated water pressure and thus a relatively high energy consumption are required. In this hydraulic final consolidation, it is customary for the energy input of the water-jet nozzles stacked one after the other to be increased from the upstream nozzles to the additional nozzles. The nozzles having the highest energy input are at the end or in the middle of the water-jet unit with regard to the travel direction of the nonwoven fleece web. In the case of nonwoven fleece web of a very high basis weight, the energy input is so high that this method is no longer feasible.
An alternative approach consists of clamping the loose mat of deposited filaments and/or nonwoven fleece web between two corotating screen belts and then performing the water-jet treatment through these screen belts. In this procedure, however, the screen belts deflect a portion of the water energy in an unfortunate manner, so that here again, the energy balance leaves much to be desired.